This application pertains to a device for determining the lateral location of an object with respect to a two-dimensional surface. More particularly, it pertains to a device for determining positions by measuring various optical characteristics of the two-dimensional surface.
In some industrial processes it is necessary to monitor the exact position of one object (normally a scanning sensor) with respect to another (normally an object being scanned). One example of such a process is inspecting a weldment by ultrasonically scanning the volume containing it. In such a process, an ultrasonic source is moved from one position to another adjacent one surface of the volume containing the weldment to be inspected. At each position, ultrasonic waves are emitted and the reflections from the workpiece are analyzed and interpreted to provide the desired information as to the quality of the weldment. Various examples of such a method are given in detail in McMasters, Non-Destructive Testing Handbook, Library of Congress No. 59-14660 (1959), especially pages 43-33 through 43-37 and 46-1 through 46-25, the disclosure of which is incorporated herein by reference. The use of the locating device of the present invention will be described herein with reference to such an ultrasonic scanning system. It should be recognized, however, that the use of the invention is not so limited and the invention may be used in connection with any system which requires information concerning the location of one object (normally a scanning sensor) with respect to a second scanning object (normally an object being scanned).
Ultrasonic techniques in use at present commonly require manual positioning of an ultrasonic source at each of many points with respect to the volume to be inspected, interpretation of the results obtained at each location, and documentation of the results. Only an extremely skilled operator can successfully obtain an accurate depiction of an internal defect in a workpiece being examined. Results are nearly always uncertain, since there is no guarantee that all of a weld has been explored. For these reasons, presently available field-operated ultrasonics equipment is not adequate for evaluating a new surface comprehensively and can only be used to monitor in-service deterioration.
Radioscopic examination, the common alternative to ultrasonics testing, has its own severe disadvantages. X-ray testing is very time consuming, requiring set up time for each exposure, time to clear the area of personnel before making the exposure, and time for developing and interpreting the exposure. In order to minimize radiation danger to personnel, X-ray inspection is generally carried out at night, requiring higher pay for the operator; in addition, night-time operation requires the operators to work in pairs for safety and results in less supervisory control of the inspection process. Moreover, X-ray films are bulky, hard to store, and costly and deteriorate relatively rapidly. In addition, an extremely high level of skill is required to interpret the exposures. For all of these reasons, radioscopic inspection is extremely expensive.